Cardiac disease and/or hypertension are increasingly common problems in animals, particularly companion and zoo animals. For example, it is estimated that approximately 10% of domesticated dogs have cardiac disease. Common cardiac diseases in dogs include primary or secondary heart diseases, such as congestive heart failure (CHF), acute CHF, chronic CHF, decompensated endocardiosis (DCE), dilated cardiomyopathy (DCM), asymptomatic (occult) CHF, asymptomatic DCM, chronic valvular heart disease. Cardiac dysfunction can be associated with shock, gastric dilation, volvulus, and myocardial ischemia. Of these conditions, chronic valvular heart disease (CVHD) (also known as myxomatous valve degeneration) is one of the more common.
CVHD is more common in female than male dogs and commonly affects the left atrioventricular or mitral valve, although the right atrioventricular or tricuspid valve is involved in about 30% of cases. The prevalence of CVHD is much higher in small dogs, e.g. dogs weighing less than 20 kg, although larger dogs may also be affected. The cause of CVHD is unknown.
The American College of Veterinary Internal Medicine (ACVIM) published a consensus statement regarding CVHD in 2009 that sets out four stages for the functional classification of heart failure, namely:                Class I describes patients with asymptomatic heart disease;        Class II describes patients with heart disease that causes clinical signs only during strenuous exercise;        Class III describes patients with heart disease that causes clinical signs with routine daily activities or mild exercise; and        Class IV describes patients with heart disease that causes severe clinical signs even at rest.        
The ACVIM consensus recommendations for treatment of CVHD include administration of an inodilator. The ACVIM has recommended twice daily administration of pimobendan, an inodilator, for the acute hospital based and chronic home based treatment of class III CVHD.
The ACVIM consensus recommendations also include treatment of chronic class Ill CVHD with furosemide, a diuretic, in addition to treatment with pimobendan. The diuretic is recommended for both acute and chronic treatment. For the acute treatment of CVHD the combination of furosemide, and pimobendan, is preferred.
The ACVIM consensus recommendations include the chronic treatment of CVHD with an angiotensin converting enzyme (ACE) inhibitor (ACE-I), such as enalapril. The evidence supporting ACE-I efficacy and safety is less clear for acute treatment of class Ill CVHD than for the chronic treatment of CVHD. Additionally, ACE-I's are useful in treatment of hypertension.
The preferred ACVIM consensus for chronic treatment of class III CVHD is administration of one or more of pimobendan, furosemide and an ACE-I.
In view of the significant problem of cardiac disease and/or hypertension there is a continuing need to develop improved formulations of active agents useful in the treatment of such conditions.